Due to the lowered fuel consumption and increased output of engines in recent years, the temperature and pressure inside the combustion chamber are on a rising trend. More precisely, the maximum explosion pressure of the engine is on a rising trend, and meanwhile the mechanical strength of the engine is tending to fall as it becomes more lightweight. As a result, during explosions inside the cylinder, the cylinder head lift is large, and the cylinder head gasket is required to have following ability with regard to that lift. If the following ability of the cylinder head gasket with regard to the cylinder head lift falls, seal leakage will occur. Another requirement is for the cylinder head lift to be restrained via the gasket.
A known method of resolving this is to make the thickness of the gasket at the cylinder hole rim portions greater than that at the other portions and increase the clamping force per unit area on the cylinder hole rim portions, so as to raise the sealing performance and restrain the amount of lift.
JP-A-8-285080 discloses a single-plate cylinder head gasket that has elastic metal plate as its material. The metal plate is formed in a particular shape to encircle each cylinder bore rim portion to an appropriate width; the remainder portion of the gasket—the portion other than the cylinder bore rim portions—is made thinner than the cylinder bore rim portions and is formed from metal plate of high hardness; and the gasket remainder portion and the cylinder bore rim portions are fitted together and the joining portions laser welded.